Need to replace the Heat Exchanger for a glow worm 38?

Can anyone help, my heat exchange has apparently cracked and is dripping water all through the electrics and filling up the under carriage. after I turned it off and drained all the water, the plumber said that it would be best to repace the entire unit with a new boiler. I am wondering if one can simply replace the heat exchanger supose of replacing the entire unit. Is this possable and if so, were would I be able to source one from. My model number is C8197 / Glowworm space saver 38 which is wall mounted. (Balanced Flur has been mentioned but I dont know what this is) If you can help by directing me were I can purchase just the Exchanger, then I can hire a plumber to come and fit it.
Thank you
Michael